Forward planning helped Rachel Osborne ascend to the top at John Lewis. Photograph: Alex Segre/Alamy

Looking at Rachel Osborne's career path you could be forgiven for thinking it had been carefully planned many years before. Starting out at the accountancy firm KPMG, she has moved steadily upwards, enjoying stints at PepsiCo, P&G and Kingfisher before joining John Lewis as financial director in 2011.

"I'm not a great planner, I've never been able to plan 10 years out," she admits. "But if you can't do that on some level you will end up boxed into a situation you can't get out of. You do tend to narrow down your options but you don't want to narrow them down too soon."

Osborne trained as a vet and credits her background in science with her ease in male-dominated environments. "It helped me to be confident in my own right and that's a key thing as you stride forward as a woman in leadership roles because there aren't that many of you. Being comfortable with that helps, and being able to still be yourself."

That confidence helped her at DIY chain B&Q, where Osborne admits the atmosphere was "blokey", although she balks at the term banter. "In America you're not even allowed to say a woman looks nice in a dress, because you'd get sued, so there's no gender associated with the culture. Blokey for me means matey, friendly, but not in a City banter kind of way," she explains.

Being yourself is key to being a successful leader, she says, because without that people won't respect your choices and you come across as disingenuous. Does she see herself as a role model? Yes and no, and not specifically for women: "I've always wanted to be a role model people can relate to, rather than a very strong female leader that people can't see any familiarity with.

"Margaret Thatcher never provided that connection for me. She wasn't someone I could say 'Yeah I get her, I feel like her'. Senior women I saw had often made compromises along the way – that's completely their choice", she adds quickly. "But they ended up either not being married or not having children. It meant that for the majority of women who do want that, there wasn't a role model for them. The more people who live that broader balance with family and children the better, it's the critical mass factor."

Children figure high on Osborne's priority list, and she admits she would much rather pass up networking opportunities in the evenings in order to be home with her family. While some senior women shy away from the topic, she is relaxed and open about how her choices have affected her career path, and the opportunities she missed as a result.

"I know I would have been overlooked for roles in PepsiCo when I had the two boys," she says, discussing her decision to tell bosses she wouldn't accept an international role in the company. "I knew when I was saying it there would be assumptions made and I couldn't influence everybody that was going to make an assumption about me, so I knew as a consequence there would be fewer roles that would be right for me in the future."

You might expect this would be a difficult pill to swallow, but Osborne explains that her time at the company was coming to a natural end. "I had half a mind that if the next role was going to be international I was going to turn it down, and I didn't want to be in that position if they offered it to me. So I made sure it was clear."

The choice wasn't just about being a woman she explains, she was influenced by colleagues she had known who had moved around internationally, and the effect it had had on marriages and children. "For me, having a sense of where you come from is important. I come from the Yorkshire Dales and that's just a part of me, so I absolutely didn't want my children to feel like international nomads, I wanted them to have a sense of belonging.

"I never thought it would close down opportunities elsewhere, but it was time to leave PepsiCo to find those opportunities. I knew I could forge a career without having to go international if I didn't want to."

Osborne's confidence is part of what sets her apart. Her ambivalence about networking and the freedom it gives her to do other things is a good example. "I'm really good at what I do," she explains. "If I want to move onwards and upwards I'd be able to get that without persuading someone through a network."

She is acutely aware of her responsibilities to the next generation of female leaders though, a far cry from the alpha "XX women" allegedly pulling the ladder up behind them. She mentors a number of women and men on an informal basis – both inside John Lewis and externally. On hearing that one of her mentees sang her praises in a recent interview, she looks momentarily surprised. "She was just in the wrong job, I helped her to see that and now she's flying – it's about giving people confidence in themselves," she says.

The culture of the business you're working in helps, Osborne explains. The idea that, if you wanted to, you could build your entire career at John Lewis breaks down barriers about career breaks and flexible working.

"People are encouraged to move around within the business," she says. "A lot of people don't necessarily examine what success means for them until later on in their careers. So early, you think the usual things – money and power – but it's really important people work out what success means to them. There's a great culture here and that support helps women to feel that they have more choices in their career, rather than a more linear progression that other companies give you. People here are just very genuine."

Asked what she would advise younger women, she recounts a conversation with a female friend, also in a senior role, who offered up the same word of warning. Perhaps unsurprisingly, it is both realistic and honest. "If you do not have flexible childcare, that will narrow the things that you can do," she says simply. "I worked really hard before I had children to get to the point where I could afford childcare. I understand why women don't want to talk about it, but the culture will never change if we're not brave. We need to be braver than we have been in the past because it might not help me, but it will help other women.

"Eventually, even if I get judged now, things will change – the culture will change and the way of thinking will change. We just have to be brave about it."